Restrictions for lock coarsening?

[Tom Rodriguez]

On Jan 6, 2009, at 11:54 AM, Clemens Eisserer wrote:

>> It's definitely an unsatisfying solution.
> Well, at least in my case it is - eliminating the possibility to
> benefit of biased locking at all :-/
> Are there ideas how the current behaviour could be changed to remove
> that restriction while not negativly influcencing startup?

I think we'd need to revisit the reason for the startup delay in the  
first place.  It's possible that other changes in biased locking have  
reduced or eliminated the penalty that the startup delay attempts to  
work around.  No one is currently looking at it and I don't believe  
our startup benchmarks are open source so external developers can't  
really run them to investigate it.  So it's a warm body problem  
tangled with some process problems.

Maybe, as I think Christian was implying, some mechanism to take  
unbiasable objects that turn out to be accessed by a single thread and  
convert them into biasable objects would be a good technical  
solution.  The basic machinery of biased locking is very much complete  
but there a still some unanswered questions policy wise that might  
result in better performance.  It would require a lot of investigation  
on someone's part though.

tom